PROJECT SUMMARY Injection drug use is the primary driver of the HIV epidemic in Southeast Asia. In 2017, the HIV prevalence among people who inject drugs (PWID) in Southeast Asia was 15%. PWID, most of whom have opiate use disorder (OUD), have low rates of HIV testing, retention in care, antiretroviral therapy (ART) initiation, and viral suppression. PWID also experience high rates of HIV-related and all-cause mortality. Common mental disorders (CMDs), including depressive, anxiety, and stress-related illnesses, occur in 40-50% of PLWH and OUD and are strongly associated with negative outcomes for HIV patients, including worsening course of HIV, more rapid progression to AIDS, increased ART non-adherence, and increased mortality rates. To respond to the great need for mental health treatment in low- and middle-income countries, the global mental health field has focused on developing task-shifting and integration approaches that equip non- specialists to deliver evidence-based mental health interventions at scale. However, such task shifting interventions to address CMDs have received limited attention in Southeast Asia among OUD. Vietnam, with its high prevalence of PLWH and OUD, its integration of methadone maintenance therapy with HIV care, and its priority for developing CMD care for this population, is an ideal setting to evaluate task-shifting mental health approaches to address CMDs and improve HIV care outcomes. The Friendship Bench (FB) is a feasible and effective task-shifting mental health intervention designed for low-resource settings that is a strong candidate to address CMDs in this population. FB is a problem solving therapy-based intervention with demonstrated effectiveness treating CMDs among primary care patients when delivered by lay counselors. Lay counselors may effectively deliver FB to PLWH with OUD, but CMD may prove more difficult to treat in patients with OUD and require professionally trained counselors to be effective. Our objective in this proposal is to complete a pilot randomized trial of 75 patients from 4 MMT clinics in Hanoi. Our specific aims are: 1) To adapt the Friendship Bench (FB) protocol to be optimized for PLWH and OUD in Vietnam; 2) To pilot the adapted FB in a three-arm individually randomized trial, comparing FB by professional counselors to FB by lay counselors to enhanced usual care for PLWH and OUD with CMDs; and 3) To assess the feasibility, fidelity, and acceptability of the adapted FB as well as preliminary indicators of its impact in improving CMD and engagement in HIV care and drug use treatment. The Friendship Bench approach has the potential to make an important contribution to address CMDs and reduce barriers to HIV treatment success among PLWH with OUD, a critical population driving the HIV epidemic in Vietnam and many Southeast Asian countries. This proposal will generate critical evidence for designing a fully powered clinical trial to test our adapted FB protocol in improving HIV, mental health, and drug use treatment outcomes for this vulnerable population.